The shield should not be put over fresh paint, yet that's what's done at many if not most coach manufacturers. It simply takes too long for paint to properly cure, literally months in this consideration, and they can't wait that long before shipping to dealers; I guess in some situations, dealers are responsible for applying the product, but yet not enough time is allowed for curing. The consequence is that the film and curing paint fuse somewhat, probably depending on ambient conditions, geographic and weather wise, following manufacture and at dealerships. This makes removing the film extra difficult, as the Shenks discovered.
A replacement should be easier to remove, if there's ever a next time, though it certainly may not be your worry by then. Nevertheless, I'd still rather have one there than not, given the likely cost of repainting the front cap. That's born out by the dozens of rock chinks in my own film, very few of which made it through to the underlying paint.
Ours hasn't yellowed, but some cloudiness is probably from the micro-scratches applied to the film, that's softer than paint, caused by poor washing techniques. Like the anti-glare films on eye glasses, it is softer and quite subject to fine scratching whereas the underlying hard surface is more resistant. Admittedly, I've not always given the cap a thorough first rinse and used soft, immaculately clean wool mitts in lieu of an auto wash brush. Dirt and road grit should be gently rinsed and then floated off with high-sudsing Dawn or other mild detergent, not brush scrubbed no matter how "soft" the brush claims or seems to be. While on trips, a weekly rinse, gentle soaping, and a simple coat of spray-on, slick, anti-bug, anti-UV, silicone or carnauba wax can help keep you from having to scrub the cap, which induces and encourages the cloudiness.
Joel